The present invention relates to a method and apparatus for transferring data over the viewable portion of a video signal, and more particularly but not exclusively to a method and apparatus that provides electronically downloadable data obtainable by optical means from a video screen.
The most common approach to applying data to a video signal currently in use is to insert data during the vertical blanking interval, such as in the generation of closed captioning signals. A major disadvantage of this method is that data in the vertical blanking interval can be removed or changed by the TV broadcaster, usually quite unintentionally, as part of the incidental operation of the broadcasting infrastructure. In certain cases the same program may be broadcast simultaneously in analog and digital formats, the data being preserved in the analog format but lost say in the digital format. Placing the data within the visual signal overcomes the problems introduced by incidental operation of the broadcasting infrastructure and thus allows a program producer to introduce data into his signal with confidence that it will be available to viewers. The program producer does not need to require the broadcaster to make changes to his broadcasting infrastructure.
An additional disadvantage of embedding data in the vertical interval is that decoding requires access to the video signal and is not possible optically using the light transmitted by the TV set. Data decoding therefore requires changes to the TV set or to the Set Top box. Embedding of the data into the screen, image ensures that data transfer does not require any modifications to the end user equipment.
In order to permit optical detection, a number of patent applications therefore teach methods of placing data on the clearly visible portion of the video signal. One advantage of the latter approach is it does not require any changes to the broadcasting infrastructure or end user equipment. Patent number WO 01/03434 A1 to Gamut Interactive describes a method for embedding data on the visible portion of a video signal. U.S. Pat. No. 6,094,228 to Koplar Interactive describes an additional method for invisibly embedding data on the visible portion of a video signal. Both approaches have been tried in the past but the methods as disclosed are limited by a narrow bandwidth, and are thus unable to support transmission of large quantities of data from the TV screen to the user's device. In practice these approaches limit possible applications of the technology to the transmission of a single code or a single identification number. The commercial coupon data itself is pre-stored in the memory of a handheld device provided to the user, and the signal embedded in the video simply triggers the appearance thereof.
International Patent Application no. WO 01/93473 A2 “Systems and Methods for Distributing Information Through Broadcast Media” to the present applicant, the contents of which are hereby incorporated by reference, discloses a method and corresponding apparatus for distribution of electronic messages that are embedded in a TV video signal. The messages may for example be data that allows printing out of coupons related to commercial material currently being broadcast. The disclosure teaches optical signals that can be embedded within the screen view and further discloses a point and click device that can be pointed at the screen to detect the signals optically. In one embodiment the point and click device includes a built-in printer. Whilst the disclosure provides a major improvement in terms of bandwidth over the prior art, it leaves open questions of the best technical method for embedding data within the video screen image in order to minimize noise, maximize bandwidth and provide the data in the most convenient and reliable manner possible to the user.